Shafiqullah Tahiri, a spokesman for the National Directorate of Security (NDS), told a news conference on March 15 that the attack could have caused massive destruction in the capital.

"According to the investigations by the National Directorate of Security experts, this truck bomb could have destroyed an area around 1.5 kilometers [in radius],” he said. “Now imagine what kind of catastrophe that would have been if [the bomb] had exploded."

Tahiri added that the attack was planned by the Al-Qaeda-linked Haqqani network and the Pakistani-based Taliban leadership. He offered no concrete evidence of the plot.

"This massive terrorist attack was planned and plotted by the Haqqani insurgent network and the [Taliban’s] Quetta Shura outside the borders of Afghanistan,” he said. “And it was fortunately prevented by National Directorate of Security officers."

Tahiri said security forces discovered the explosives during a night raid earlier this week. The explosives were hidden in cement bags in a truck in eastern Kabul.

According to Tahiri, security forces killed five suspected plotters and arrested two others. He said the militants had been planning to target a military facility in the capital.

News of the plot comes almost a week after a suicide bomber blew himself up outside the Defense Ministry in Kabul. That attack killed nine people while U.S. Secretary of Defense Chuck Hagel was visiting a NATO facility nearby.

It also comes amid serious strains in U.S.-Afghan relations as NATO-led combat troops prepare to withdraw from Afghanistan by the end of 2014.

This week, the top U.S. commander in Afghanistan, Joseph Dunford, warned about the increased risk of attacks by militants and rogue Afghan soldiers because of a series of inflammatory anti-American remarks by Afghan President Hamid Karzai.

On March 10, Karzai accused the United States of colluding with the Taliban to keep the country unstable and give foreign forces an excuse to stay beyond 2014.

A statement from Karzai's office on March 14 said the president wanted to "correct" rather than damage U.S.-Afghan relations.